There are conventional gas-operated firearms with a gas block mounted on the barrel. In the conventional gas block a portion of high-pressure gas is pushing an operation rod, and the gas block is experiencing a reaction in the opposite direction. As a result, the movement of the gas block is affecting the barrel. This leads to vibrations of the barrel and the reduction of aiming accuracy. See FIG. 1, where the barrel is 3, the gas block is 2 and the operation rod is 15. An impact of the shooting is causing gas pulses going into the gas block. Since the firing of the bullets occurs in rapid succession at a rate of hundreds of bullets per minute, the barrel is shaking, and thus the accuracy of aiming is dramatically affected. It would be beneficial to reduce the barrel vibrations and rotations.
A few prior patent applications, US 2014/0224114 and US 2011/0271827, address a connection between the gas block and upper receiver but only via a rail on which the gas block can slide. The gas block does not have any rigid fixation to the receiver, there is still a gap between the receiver and the gas block, and the gas pulse impact is not neutralized by the receiver. The receiver does not use its mass (combined with the mass of the shooter or the support of the firearm) to neutralize the impact.
At present, the idea of modular weapons has become popular. By replacing the barrel, bolt and magazine, one can change the caliber of the used magazines. Often, magazines of different calibers have a different design. This requires the use of various magazine wells. A lower receiver is typically mounted to the upper receiver using pins. U.S. Pat. No. 7,810,271 discloses a similar idea: its trigger house is connected to the magazine well and to the upper receiver using pins and apertures. In practice, the existing gaps and gradual wear lead to loosening of this joint and disruption of the mechanisms. A new solution is also required to solve this problem.